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The circadian clock sets the pace of plant growth

19 Feb

Scheme representing the levels of the different PRR proteins and the activity of the PIF protein during the 24 hour cycle. Below it represents how these proteins affect the growth of the Arabidopsis seedling (Credit: Guiomar Martín & Judit Soy)

BEES academic Dr Rossana Henriques has published, with colleagues, a new paper detailiing their discovery that the members of a protein family from the plant internal clock act sequentially to limit the plant growth until the end of the night. This knowledge could help to understand how plants face different kinds of stress that affect their growth, such as drought or high temperature.

The circadian clock is an internal timekeeping mechanism that allows plants to adjust their biological processes to 24h days. Together with photosensory pathways, the clock regulates the timing of plant growth to the end of the night in plants grown under short days (8h light / 16h dark). This diurnal pattern of growth was shown to depend on a specific set of transcription factors the PHYTOCHROME-INTERACTING FACTORS (PIFs). However, although PIFs could be detected during the day, they accumulated mostly at night and their growth-promoting function only occurred pre-dawn.

In this report Martín et al. elucidate the mechanism behind this regulation. PIFs proteins were shown to directly interact with PRR (PSEUDO-RESPONSE REGULATOR) proteins that will inhibit their activity during the day. At night PIFs are free to induce expression of growth promoting genes, such as CDF5 (CYCLING DOF FACTOR 5). These findings explain how the circadian clock, through PRRs’ inhibition of PIF activity, gates growth responses to the adequate time of the day. They also provide candidate proteins for this regulation and allow for future identification and characterization of critical growth regulators in agronomical relevant crops.

This work was developed at CRAG (Barcelona, Spain) under the coordination of Dr Elena Monte in collaboration with Dr Rossana Henriques (School of BEES, UCC), as well as with researchers from the University of Lancaster, the University of Edinburgh, the Institute for Plant Molecular and Cell Biology (Valencia, Spain) and the Chemical Institute of Sarria (Barcelona, Spain).